Proximity inductor heating and quenching fixture



,w. H. LENZ 3,122,625

PROXIMITY INDUCTOR HEATING AND QUENCHING FIXTURE Feb. 25, 1964 Filed Jan. 19, 1962 2 Sheets-Sheet 1 m ll |h r INVENTOR. WA LTER H. LE/vz Feb. 25, 1964 w. H. LENZ 3,122,625

I PROXIMITY INDUCTOR HEATING AND QUENCHING FIXTURE Filed Jan. 19, 1962 2 Sheets-Sheet 2 INVENTOR. WALTER LE/vz A TTORNE'YS United States Patent 3,122,625 PROXIMETY INDU CTOR HEATING AND QUENCHKNG FIXTURE Walter H. Lena, Washington, Ill., assignor to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed Jan. 19, 1962, Ser. No. 167,282 3 Claims. (Cl. 21.9-10.43)

The present invention relates to apparatus for the heat treatment of metallic work pieces and more particularly to apparatus for heat treating specific portions of large arcuate members, such as gears.

The excessive rate of wear of the internal gear teeth of blade support circles used with construction equipment such as motor graders, has presented a problem of long standing. Until the present invention, apparatus for economically heat treating specific portions of large complex structures such as the internal teeth of blade support circles has not been available, and has therefore required the continued tolerance of the above mentioned problem.

Accordingly, it is the object of the present invention to provide heat treating apparatus capable of economically heat treating specified portions of large arcuate members of complex structure such as blade support circles used on motor graders.

:Further and more specific objects and advantages of the invention are made apparent in the following specification wherein a preferred form of the invention is described by reference to the accompanying drawings.

in the drawings:

FIG. 1 is a plan view of a motor grader drawbar, blade support, and drive mechanism therefor;

FIG. 2 is an enlarged sectional view taken through the line iI-II of FIG. 1;

FIG. 3 is a plan view of the heat treating apparatus of the present invention operating on the internal gear teeth of a blade support circle; and

EEG. 4 is an enlarged sectional view taken on the line iV--IV of FIG. 3.

Referring now to FIG. 1, there is shown a drawbar -11 secured to a "heavy annulus or drawbar ring '12. Disposed concentrically to ring 12 is a blade support circle 15 which has internal gear teeth .13. Rigidly secured to circle 15 is a blade "14-, the angular position of which is adjusted by rotation of the blade support circle. A spreader bar 16 secured to ring 12 is connected to linkage (not shown) by means of ball portions 17 for the purpose of raising or lowering the blade or tilting it to a desired angle. To alter the angular position of the blade, a spur gear 13 meshing with the internal teeth 13 of circle 15 is rotated until the desired angle is reached. Thus, the resistive load to rotating circle 15 is counteracted by one or two of the internal teeth 13. When this load becomes extreme, it is not uncommon for the hardened spur gear 18 to cause peening or extrusion of the circle gear teeth 13.

Referring now to FIG. 2, blade circle '15 is supported by a plurality of arcuate support shoes 19 connected to drawbar ring 12. it is apparent that peening or extrusion of any of the gear teeth 13 is likely to prevent the smooth rotation of circle 15 with respect to shoes 19 and thereby induce high wear of the teeth if not prevent rotation a1- together. i

The above description with reference to FIGS. 1 and 2 illustrates one oi many uses of large arcuate gears and the problems which are encountered when they cannot be economically heat treated so as to withstand damage when meshing with hardened gears. While the present invention is particularly applicable for heat treating the internal gear teeth of motor grader blade support circles, and is described with reference thereto, it will be seen 3,122,625 Patented Feb. 25, 1964 from the description which follows that its utility extends generally to large metal arcuate structures having portions not separably heat treatable by apparatus now known in the art. 5

Referring now to FIGS. 3 and 4, there is shown apparatus capable of receiving members such as ring gear 15, heating a specified portion thereof, and subjecting the heated portion to a quenching medium; all in a quick, economical manner suitable for production line operation. Ring gear 15 is placed on an annular support member 21 in a shallow quench tank 22 such that gear teeth 13 of ring 15 reside in the lower portion of the tank and are disposed radially inwardly of support 21. In this position teeth 13 do not bear any of the weight of ring 15 and are free to receive quenching medium from below as will be further described in detail. The correct alignment of ring 15 on support 21 is important if the proper heating and quenching is to occur. For enabling correct alignment to be quickly established, a series of guide members 23, approximately 180 apart are secured within tank 22. Two of these guides have a protruding finger 23a. The distance between the ends of fingers 23a is such as to register with two selected tooth roots on the gear as indicated at 23a. With this alignment of the ring member, the remainder of the heat treating apparatus may be fixed in place in proper relationship to the gear. Fingers 23a are radially adjustable to be useful for gears of varying sizes and also prevent rotation of gear 15 once it is properly aligned.

A pair of hollow arcuate conductors 24 and 25 are disposed radially inwardly from and in close proximity to gear teeth 13 when ring 15 is properly aligned on support 21. Each of the arcuate conductors extends through an angle of approximately and together combine to heat approximately half of a circular member in one position. While it is within the teachings of the invention to provide apparatus for heating the entire ring at once, it has been found more practical to treat one half of the ring at a time. p

The conductors are athxed on semi-circular support member 26 which is made of an insulating material. Each conductor is attached to member 26 in three places, and each attachment is of a ditierent type to perform a slightly different function. Brackets 27 are disposed on either side of the circumferential mid-point of support member 26 and rigidly secure the conductors to the member at those points. At a point approximately half way between brackets 27 and the ends of member 26, a pair of spring loaded clamps 28 connect the conductors to their support member. Clamps 28 are representative of any connection means which exerts force which urges a movable member toward a fixed member, while the members may be. further separated. when forces are exerted which counteract the clamp forces. Springs 28a provide the force urging conductors 2e and 25 toward member 26.

At the ends of semi-circular support member 26 are a pair of pneumatically operated plunger mechanisms 61 (pneumatic source not shown) which urge the associated ends of conductors 24 and 25 respectively away from support member 26 and toward the work piece 15. Each of plunger mechanisms 31 comprises a piston 32 in a cylinder 33 which is rigidly mounted radially inward from member 26. A piston rod 34 extends through member 26 and anchors in a block 36 which is secured to the associated conductor. Block 36 fits Within a recess 37 in the support member so that the conductor can be positioned flush with its support 26 when desired. When piston 3:2 is extended, however, conduits 24 and 25 are forced away from support member 26 into contact with the work piece.

Secured to conductors 24 and 25 at the same positions as blocks as but on the other side of the conductors are a pair of electrodes 33 and 39, respectively. When ring has been placed on support 21, pistons 32 are extended until the electrodes engage the work piece. By virtue of the manner in which the conductors are secured to support 26, there will be a generally uniform spacing between the work piece and the conductors when the electrodes engage the surface of the gear teeth. This allows the apparatus to accommodate gears varying in size, without requiring major adjustment of the components or loss of operating efliciency. Electrodes 38 and 39' are so spaced from guides 23 that they are assured of engaging a gear tooth (the importance of which will be clear later) rather than a surface therebetween. When it is necessary or desired to alter the space between the arcuate conductors and the work piece, electrodes 38 and 39 are replaced by electrodes of different thickness.

Between brackets 27 conductors 24 and 25 have hollow extensions 24a and 25a, respectively, which are directed radially inward and connect with hollow electrical conduits 41 and 42 (as best shown in FIG. 4) leading to electrical energy source 43. Extensions 24a and 25a are electrically separated by an insulating member 44 disposed therebetween, which also separates the vertical portions 41a and 42a of conduits 41 and 42. Between source 43 and the conduits leading thereto, there is a unit 4-6 for controlling the output of source 43.

The electrical components described above, source 43, control unit 46, conduits 41 and 42, conductors 24 and 25, and electrodes 38 and 39, form an incomplete (open) circuit incapable of passing a current. When ring 15 is positioned on support 21 and plungers 31 activated to urge electrodes 38 and 39 in contact with internal gear teeth, the ring becomes part of the electrical circuit of the apparatus and completes (closes) it so as to allow current to flow. Source 43 is of the type which furnishes high frequency (10,000 to 100,000 c.p.s.) current. Current from source 43 flows through the completed circuit via the following path: conduit 41, to extension 24a, to arcuate conductor 24, to electrode 38, to ring 15, to electrode 39 (clockwise), to arcuate conductor 25, to extension 25a, to conduit 42 and back to source 43. This current path establishes a current flow in work piece 15 which is opposite in direction to the current flow in the adjacent arcuate inductors. The magnetic flux produced as a result of the current flowing through arcuate conductor 24, for example, will be opposite to that produced by the current flowing through the adjacent portion of ring 15 and have the effect of suppressing the flux from member 15. Suppressing the flux from member 15 greatly reduces its inductance. Since the density of the flux from the arcuate conductors decreases with distance from the conductor, the suppression of flux and the accompanying reduction of induction of member 15 will be limited to the inner radial portions, the exact extent being dependent upon the radial distance between member 15 and the arcuate conductors.

The major factor in retarding current flow in large metal members such as gear '15 is the inductance of the member, not the resistance. When two electrodes at different potentials are in contact with a large metal object, the current flow will be restricted, almost entirely, to a path between the electrodes which is of less inductance than any other path. If no such path exists, the current path will be distributed equally throughout the member. As described above, the apparatus of the present invention creates a path of reduced inductance in member 15 between electrodes 38 and 39. As a consequence, the current flowing between the electrodes travels almost exclusively through the gear teeth 13. Although the inductance of member 15 controls the current path followed, there is an amount of resistance (as there is in almost any real object) in any path between the electrodes so that current flow therethrough results in resistive heat generation. By supplying currents of high magnitude, teeth 13 (through which the current flows) can be heat treated without the necessity of heating the other portions of member 15.

In addition to the electrical system described above, the present invention provides an integrated fluid system for cooling the current carrying conductors and supplying a directed quench system. Cooling of the hollow conductors 24 and 25 is accomplished in a conventional manner by introducing fluid at the extensions 24a and 25a through a pair of lines 51 which are supplied with fluid from a source (not shown) at intake 52. The fluid circulates through the arcuate conductors and then passes through flexible tubes 53 connected at the ends thereof to a discharge valve 54, returning the fluid to the source. The medium employed for quenching the gear teeth 13 is introduced through a pair of pipes 56 and 57 to a chamber 58 formed by the bottom of tank 22, and an annular platform 59 supported by annular spacers 61. Disposed on platform 59 are conductor support member 26 and gear ring support member 21.

When the quenching stage of the heat treatment operation is desired the quenching medium is introduced through pipes 56 and 57 to chamber 58. A plurality of orifices 62 in platform 59' are disposed such that quenching media from chamber 58 is sprayed on each individual tooth 13. The orifices in platform 59 are situated to direct quenching media against each tooth of gear 15. In this manner it is not necessary for a large quantity of quenching media to be employed or to immerse the entire work piece, as is the practice in many similar operations. This gives a saving in time as well as quench fluid. A drain 63 returns the quenching medium to its source (not shown) or disposes of it, depending upon the operation being performed.

A housing structure 64 is provided around the ends of extensions 24a and 25a and associated conduits 41 and 42 to prevent the quenching medium from contacting these current carrying members.

As previously mentioned, ring gear 15 has been described in connection with the present invention, only as one of many possible arcuate members to which the present invention applies. The nature of the internal surface (irregular, smooth, etc.) is not limiting on the applicability of the invention. Although the specific apparatus shown in FZGS. 3 and 4 is not equipped to treat outer circumferential surfaces, the general teaching in connection therewith is sufficient for one familiar with the art to easily make the necessary modifications to enable the apparatus to perform such operations.

I claim:

1. In apparatus for heating an internal portion of an arcuate metal work piece the combination comprising:

a pair of arcuate conductors disposed concentric to and radially inward from the work piece, said conductors having a pair of adjacent ends and a pair of remote ends;

means securing said conductors in a fixed position at their adjacent ends;

means for urging the remote ends of said conductors radially outward;

a pair of electrodes, one on each of the remote ends of said conductors, said electrodes urged into engagement with the work piece when the remote ends of the conductors are urged outward; and

a source of high frequency current electrically connected to the adjacent ends of said conductors;

said conductors spaced from said work piece such that current flowing therethrough is restricted to the internal portion to be heated.

2. The apparatus of claim 1 having means for spraying quench media on the internal portion of the work piece to be treated, and means for cooling said conductors.

3. In apparatus for heat treating circular gears the combination comprising:

a pair of arcuate conductors disposed to form a semicircle wherein the semi-circle has a. smaller diameter than the gears to be treated, said conductors having adjacent ends and remote ends;

means securing the adjacent ends of said conductors in a fixed location;

an electrode secured at the remote end of each of said conductors;

means for urging the remote ends of said conductors radially outward to engage the inner surface of a gear placed in a concentric relationship to said conductors;

guide means disposed to receive gears to be treated and effective to align the gear relative to said conductors such that the distance between said conductors and the adjacent portion of the gear is generally uniform and the circumferential disposition of the gear is such that said electrodes engage the gear at the face of a tooth thereof; and

a source of high frequency current electrically connected to the adjacent ends of said conductors.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN APPARATUS FOR HEATING AN INTERNAL PORTION OF AN ARCUATE METAL WORK PIECE THE COMBINATION COMPRISING: A PAIR OF ARCUATE CONDUCTORS DISPOSED CONCENTRIC TO AND RADIALLY INWARD FROM THE WORK PIECE, SAID CONDUCTORS HAVING A PAIR OF ADJACENT ENDS AND A PAIR OF REMOTE ENDS; MEANS SECURING SAID CONDUCTORS IN A FIXED POSITION AT THEIR ADJACENT ENDS; MEANS FOR URGING THE REMOTE ENDS OF SAID CONDUCTORS RADIALLY OUTWARD; A PAIR OF ELECTRODES, ONE ON EACH OF THE REMOTE ENDS OF SAID CONDUCTORS, SAID ELECTRODES URGED INTO ENGAGEMENT WITH THE WORK PIECE WHEN THE REMOTE ENDS OF THE CONDUCTORS ARE URGED OUTWARD; AND A SOURCE OF HIGH FREQUENCY CURRENT ELECTRICALLY CONNECTED TO THE ADJACENT ENDS OF SAID CONDUCTORS; SAID CONDUCTORS SPACED FROM SAID WORK PIECE SUCH THAT CURRENT FLOWING THERETHROUGH IS RESTRICTED TO THE INTERNAL PORTION TO BE HEATED. 